The how to of soil samples

Soil Sampling Pastures

Collecting a soil sample in your pasture is an important first step in determining the nutrients needs of your pasture. Your goals of a soil sampling plan should be::

• Identify manageable size pastures typically of less than 20 acres that have similar characteristics
• Figure out the nutrient needs of your pasture accurately and in an efficient manner

Variable soil conditions across a pasture make it difficult to have a good soil sample, however with good planning a typical example of the soil may be collected from your pasture.

The high cost of fertilizer requires that you have a complete soil analysis in order to make efficient use of fertilizer nutrients (nitrogen, phosphorus, potassium: N-P-K ) available. You want a fertilizer mixture created that will be just right for the soil needs of your pasture. A proper soil sample will enable Pasture Services to create just the right fertilizer mixture for your pasture.

Dividing your pasture for soil sampling?

When planning to sample the soil in your pasture, the objective is to divide the pasture into sections that are the same or that you manage differently.

The typical sampling area would normally not exceed 20 acres.

Pastures can be extremely variable in terms of nutrient needs, just think of the following when planning to collect a soil sample::

• Livestock movement, resting and feeding areas create a wide variation in the pasture.
  • Note that manure piles and urine spots will have elevated nutrient levels.
  • Areas of winter feeding, resting areas and water sources also tend to test different that the rest of the pasture.
• The topography and soil type of a pasture can create variability especially in unfertilized pastures.

The goal of pasture soil sampling is to avoid areas that are non-typical in the pasture. Avoid taking soil samples near feeding areas, resting areas like around shade trees or water sources. These areas will tend to be higher in nutrients due to animal concentrations.

Plan to collect a good soil sample

The idea is to collect 15 to 20 samples of the soil in your pasture. This is more that you would typically take in a crop field because in a pasture you are going to have manure and urine spots which will skew the analysis.

It is a good idea to travel randomly around your pasture to collect soil samples. Avoid areas around water holes, shade trees, feeding areas or salt licks as these will tend to be places where the livestock congregates.

The objective for a pasture is to take soil samples to a depth of 6 to 7 inches. A shallow sample will overestimate the fertility in your pasture.

Typically in a cultivated field you take a deep bore sample by pushing a hollow core rod into the ground. However unless you have a boring machine to force the core into the ground this is not a good plan for a pasture.

We have found the ideal and very simple procedure for taking a 6 to 7 inch core sample is a battery powered drill plus an old wood bit. The one used here is left over from my grandfather's day. It is an old hand powered wood bit with the end cut off so it would fit the chuck of the drill.

A power drill facilitates sampling in rocky or dry soils. This is probably the ideal sampling tool in the Bitterroot Valley. Remove the organic material from the surface of the selected soil testing area. Then take a small plastic container and drill right thru the bottom of it. This creates a hole to draw your soil sample thru.

For demonstration purposes we are showing an old bucket lid. Note that it is essential to press the lid firmly to the ground at the spot you wish to core. This then forces the core sample to be drawn to the lid surface so it can be added to the rest of your core samples.

So the equipment needed to collect a soil sample is as follows:

1. A clean plastic bucket (like old ice cream container) to draw the core sample through.

2. Another clean plastic bucket to collect all your soil samples.

3. A baggie or small paper sack to transfer your soil samples to, for delivery to Pasture Services for analysis.

Break up the 15 to 20 cores and thoroughly mix the soil. If your soil sample has moisture in it, spread it out to dry in an old pan before transferring to a baggie or sack. Wet or damp soil samples cause problems with shipping to the laboratory for analysis. Place about 1.5 cups of the mixture into a soil sample box or plastic bag and discard the excess.

Sample your pasture every three to five years. It is better to do a more thorough job of sampling with more cores per sample less often than to do a poor job more often.

Submitting your soil samples

Label the sample with field identification and submit to Pasture Services at Mountain West Co-op in 115 Main Stevensville, Mt. 59870 or Mountain West Co-op 4570 North Reserve, Missoula, Mt. 59801